1. Field of the Invention
The present invention relates to a vehicle control system, a vehicle control method, and a vehicle control program.
2. Description of the Related Art
Conventionally, a vehicle control system is studied that automatically determines the control item of a running vehicle, based on a vehicle current position. For example, a system disclosed in Japanese Patent Laid-Open Publication No. 2005-132291 determines a current position of a vehicle according to a radio wave navigation based on the received information of a GPS (Global Positioning System) radio wave and a hybrid navigation based on an autonomous navigation based on information acquired by the vehicle without using the GPS radio wave. Then depending on the likelihood (degree of certainty) of the current position, the system changes the control item of the vehicle.
However, according to the method of using the GPS radio wave, there often occur cases that a driver himself/herself manually drives his/her vehicle, canceling the control of the vehicle when the reception environment of the GPS radio wave becomes worse. Thus the driver is forced to manually drive the vehicle every time when the vehicle control is cancelled, and therefore the usability of the vehicle control is bad.
In addition, in such a case of passing through a high-rise building block, the influence of the GPS accuracy worsening appears due to a radio wave around the vehicle. As a result thereof, such a number of GPS receiving satellites is reduced, and the certainty of a vehicle current position is worsened.
Accordingly, with respect to the accuracy worsening due to the reception environment of the GPS radio wave, because it is not forecasted when the accuracy is worsened, the continuity of the vehicle control cannot be kept and there is no way other than canceling the vehicle control. Although a method of simulating an operation situation of a GPS satellite in advance can also be thought, in practical it is not realistic, considering the influence of multi-paths due to the reflection and the ever-changing of a real environment in such a real building block.
On the other hand, the method of determining a vehicle current position only by an autonomous navigation without using the GPS radio wave. The autonomous navigation has an advantage of being difficult to be influenced by the receiving environment of the GPS radio wave. However, because the autonomous navigation is the method of accumulating a movement distance calculated from a speed and a direction measured by a driver's own vehicle, an error between a vehicle current position calculated by the autonomous navigation and an original vehicle current position is accumulated as the movement distance becomes longer.
It is not desirable to execute a sophisticated vehicle control when the error is large (in other words, the degree of certainty is bad). Accordingly, when the error is large, a vehicle control should be taken that is not sophisticated such a deceleration. Furthermore, the accuracy of a vehicle current position whose target is a vehicle control is needed to be higher than that of a vehicle current position whose target is the map matching of a car-navi (car navigation).
In the conventional determination method of a driver's own vehicle current position whose target is the map matching, a map display is a precondition; therefore, the vehicle current position is determined, then the processing of the map matching is executed, and the vehicle current position on the map is determined. In the processing of the map matching, because an association between a road on an erroneous map and a running position using the map, there is a possibility that the map matching is forcibly matched with a nearest road. This is because a judgment is conventionally taken that the slight difference of a display position does not become a critical problem since the map display is made the precondition.
Consequently, there is a need for providing a driver with a convenience by broadening the control range of a vehicle control, based on the calculation error of a vehicle current position.